EXP2_01_PIN for BTT BTT002 1.0

Marlin/src/pins/stm32f4/pins_BTT_BTT002_V1_0.h

@@ -194,6 +194,7 @@
 #define EXP1_09_PIN                         PB1
 #define EXP1_10_PIN                         PE7
 
+#define EXP2_01_PIN                         PA3
 #define EXP2_03_PIN                         -1
 #define EXP2_04_PIN                         PC4
 #define EXP2_05_PIN                         PA7